A composite image that combines data obtained from the Hubble Space Telescope and the Pan-STARRS1 telescope in Hawaii shows the details of the planetary nebula Abell 78. It’s rather unusual among planetary nebulae because it’s a so-called born again star whose core stopped nuclear fusion but the density reached by the external layers ejected in a violent way triggered the fusion of helium in them. The consequence is an even more violent ejection of materials that generated the nebula’s irregular shape around the now dying progenitor star.

About 5,000 light-years from Earth, the planetary nebula Abell 78, also known as ACO 78, PK 081-14.1, ARO 174, and with other designations in various catalogs, represents an interesting object of study due to its unusual characteristics. When a small to medium-mass star approaches the end of its life and nuclear fusion stopped in its core, it begins to collapse while the outer layers are ejected and form a planetary nebula. The result is spectacular and at the same time interesting from a scientific point of view.

A planetary nebula has a limited life span in astronomical terms because over millennia the materials ejected from the star disperse into interstellar space and cool down. However, in some cases, the outer layers are ejected with such violence as to trigger thermonuclear reactions that lead to the object being called a born again star. The materials projected outwards in an even more violent and chaotic way hit those previously ejected, generating irregular shapes like that of Abell 78.

Images of the Abell 78 planetary nebula captured with the Hubble Space Telescope’s Wide Field Camera 3 (WFC3) and with the 1.4 Gigapixel (GPC1) camera mounted on the 1.8-meter Pan-STARRS1 (Panoramic Survey Telescope) and Rapid Response System) at various optical frequencies were combined to form the new image.

The resulting image reveals many details of Abell 78. The halo is composed mostly of hydrogen and helium, but the color hues also indicate which elements were produced by the surface nuclear fusion. Spectroscopic analyzes can provide more information in this regard, but the images are useful in various ways and offer a breathtaking show even by the standards of planetary nebulae.